1. Field of the Invention
The present invention relates to a dynamically balanced centrifugal fan and a method for balancing such a fan. More particularly, the present invention relates to a dynamically balanced centrifugal fan having a fan inlet ring in which the radial thickness of ring is varied to correct imbalance of the fan.
2. Disclosure Information
Centrifugal fans can be utilized for a variety of applications where air movement is needed, such as the ventilation system in an automotive vehicle. Centrifugal fans are typically molded from a synthetic polymeric material to reduce weight, reduce manufacturing cost, and ease assembly into a system. Typically, molded plastic fans must be balanced during the manufacturing process and typically this is done through a selective distribution of plastic material within the mold used to manufacture the fan. Other post-molding balancing practices include the addition of weights to the fan, such as with clips.
Since plastic fans are usually manufactured by an injection molding process, the fans can be dynamically balanced during that process once the zone and magnitude of the imbalance is determined. Typical methods for balancing plastic fans in an injection molding process have involved machining away material from a predetermined location of the mold to increase the amount and increase the weight of plastic at these locations by allowing additional plastic to be added to obtain the desired balanced weight distribution. While this method has been proven to be acceptable, continued machining away of material and the mold ultimately destroys the mold forcing the fabrication of a new one.
Other attempts to dynamically balance fans during a molding process involve the use of screws located at fixed points within the mold. Once a fan has been determined to be imbalanced, the screws can be changed to allow more or less plastic material to flow into the threaded aperture of the screw to provide more or less weight at specific locations to change the balance of the fan. Typically, the screws are located at fixed locations in the mold such that the thickness of a portion of the fan is changing in a generally vertical plane in an axial direction relative to the rotational axis of the centrifugal fans. While this method has been proven to be useful, it involves a substantial amount of "trial and error" of moving a multiple number of threaded screws to achieve the balance needed for the fan.
Therefore, it would be desirable to provide a method for balancing a centrifugal fan which does not require machining away of the fan mold and which can be accomplished quickly and easily. It is an object of the present invention to provide a method for dynamically balancing a fan in a radial direction, not vertically in an axial direction.